New Scientist has the details of this incredible image of the Sun taken over the course of six months with a pinhole camera. Taken by Justin Quinnell, it shows the path of the Sun from winter to sumer over Bristol in the UK. Each arc is the Sun, blurred by its daily motion, and the differing heights of the arcs shows how the Sun’s position in the sky changes with seasons.

Pinhole cameras are very cool; the hole is so small that any light rays from a small object entering it and hitting the film are naturally very close to parallel, and therefore in focus. You don’t need a lens! It’s similar to the depth-of-field issue versus aperture in a regular camera. Anyway, this is a very cool shot, and you should check out the New Scientist page, since it has more info, including links on how to do this yourself.

I love this stuff. Camera Obscuras are cool too. I proved to myself once long ago the the principle of projecting an image (without electronics) can be applied to astronomy by once setting up a contraption of telescope and separate lens on a balcony in order to project a pretty good clear image of the moon on the ceiling of an apartment I had at the time. Even in a dark room the stars were too faint but the bright moon looked mighty impressive, all the lunar “seas” and big craters could be seen – though it all moved cross the room pretty fast! (A clock drive was not available.)

I used to live in Bristol, and I know this place – the Clifton Suspension Bridge, built by I K Brunel. There is actually a rather fun camera obscura in a small tower nearby, in which you can turn the turret to get different views of the gorge and the bridge. But I don’t suppose that was used, as it would have had to be closed to the public for months.

That’s really cool. I didn’t know that was how pinhole cameras worked, what a simple explanation.

Also, I just finished reading your first book, Bad Astronomy. I really enjoyed it, and, while I knew tides were caused by the moon’s and the Sun’s gravity, I didn’t know what caused two tides a day until I read it from you. That’s not the only thing I learned, there were other things as well. So thanks!

For anyone who is interested, it was the 10th-century Arab physicist, astronomer and mathematician, Ibn al-Haytham (Alhazen), who published the principle of the pinhole camera in the Book of Optics in 1021 AD. He also invented the first pinhole camera after noticing the way light was streaming through a hole in a window shutter. He improved on the camera after realizing that the smaller the pinhole, the sharper the image (though the less light). He designed the first camera obscura (Latin: dark chamber). As a side benefit of his invention, he was credited with being the first man to shift physics from a philosophical to an experimental basis.

For more information on the physics of a pinhole camera, click on my name above this post.

P.S. Imagine what other advancements in the field of physics the Arabs might have achieved if they had not found religion in the form of Islam!

On a related note, do you know that you have a magnifying lens at your fingertips?

Try this. Pick a very tiny object that you can focus on comfortably. Note its apparent size. Then touch index finger to thumb on both hands, like making an “OK” gesture. Now, bring both pairs together so that both index fingers and thumbs touch. You will observe an opening between the four digits. Press them tighter to reduce the opening and bring your eye closer to it. Make the small hole as small as you can see through and look at the object again.

Move the aperture and your eyes relative to the object until you have reasonable focus. Surprise! You now have a super power!

The photographer’s site includes instructions on making pinhole cameras, including the 720-degree toilet-roll camera(!). (BTW, besides his 6-month exposures, he also seems to have a thing about taking pictures from inside his mouth. WTF?)

See also Tarja Trygg’s Solargraphy site for images like this from all over the world.

Flickr is loaded with pinhole camera aficionados, including quite a few groups. Quite a few people over there are building their own or modding everything from cheap disposables to DSLRs. Crazy fun.

I tried to make a pinhole camera as an extra grade project in high school (we still used candlelight and hourse drawn carriages back then). I gave up trying after sticking the pin in my leg. Everyone in class thought it was funny. But, then I really didn’t want to take pictures of teacher and classmates anyway. An ungly lot, them.

Tarja Trygg has maintained a website about this technique for several years at http://www.solargraphy.com/ including a gallery of photos taken by people all over the world.
The image is on an undeveloped piece of photographic paper. The image is made by the action of light alone. Because the particles of silver are smaller than in a developed photo and various sizes due to varying exposure, they look different colors on the negative (I think it’s an interference thing). In any event, when reversed, the sky is blue and often looks like relatively realistic color.

The rays aren’t parallel, it’s that there is minimal parallax due to the width of the aperture.

Yes, I was just going to complain about “pinhead astronomy” in my drive by comment. AFAIU a focus is where rays from an object point converge to an image point. The picture I get is that an ideal pinhole provides focus by mapping visible object points to image points onto (i.e. 1-1). In fact, I see that is the image [pun intended] provided in Wikipedia.

It seems to me the ideal model would explain if a pinhole camera has ideally an infinite (or perhaps indefinite) focal length, and inverts the image. I assume using the physical width of the aperture gives a correction to a best focal length. But if rays from small objects were “parallel” they would give no focus and tend to blur the image, wouldn’t they, besides not explaining image inversion?

But I’m not giving this a lot of thought due to time constraints, so I could be _very_ wrong.

Ok. I give up. I know the earth goes around the sun in an ellipse so the solar day is not 24 hrs long (shorter near periphelion) and longer at aphelion.) But WHY in this picture does the sun rise at the same point day after day and set at different points? And it sets skimming the horizon, whereas it comes straight up.

Ok. I give up. I know the earth goes around the sun in an ellipse so the solar day is not 24 hrs long (shorter near periphelion) and longer at aphelion.) But WHY in this picture does the sun rise at the same point day after day and set at different points? And it sets skimming the horizon, whereas it comes straight up.
I may well have submitted this; I was racing outside to see the second sonic boom so I don’t know if this went through.
I am resubmitting in order to ask the second question. Why is the point of maximal elevation of the sun changing? Due south changes as the year progresses?
Unless my understanding of the spherical trig is wrong (it shouldn’t be–I was the only one getting the spherical trig questions about the sun right in trig class), there is some fundamental fudge in this picture–like the non smudged bridge maybe? IOW did he move the camera?

I agree with mighty favog. All rays entering any camera from a distance are nearly parallel, so that’s irrelevant.

Theoretically, if all light from the landscape were to enter the camera through the very same point (the size of one photon?), the image on the film side would be in perfect symmetry with the real world, and so the picture would be infinitely sharp.

But then again, (almost?) no light would make it through this pointhole, so I suppose that exposure time would have to approach infinite, too. Or maybe there are some weird quantum effects that I’m completely ignoring.

Is the screwy geometry of the sun’s path some manifestation of projective geometry? I’m not very fond of projective geometry, but if no one posts an answer I guess I’ll have to investigate.
I can understand the point of highest elevation being an effect of projective geometry; but I can’t see any reason for the sun coming up straight at sunrise (and from the same point!) and grazing the horizon at sunset.

There are only about 30 tracks, so roughly speaking he took the camera in and then out again about a week later (presumably on a day the weather should be good. The weather has roughly a 7 day period.) But he seems to have had some strange algorithm for how he was going to line it up (he didn’t line it up on the bridge–the bridge was exposed only on one day or so, maybe a few days, there is a gap above the bridge that might be the bridge obscuring part of one track; he seems to have obscured the horizon most days). He seems to have lined it up according to the rising of the sun so that the sun always rose at the same spot. Then in the summer when the sun skims the horizon in northern latitudes, the arc curved toward the horizon in the sun’s setting sequence. A pity he didn’t have a translucent paper with an image of the bridge on which to align or better yet on some object due south of his location.
BTW re overexposure–film solarizes so white becomes black and approximately vv.

The “screwy geometry” of the sun’s path is a result of the image being recorced on a curved film plane. Typically these cameras are made from 35mm film canisters. Imagine looking down at the film canister. The pinhole is at the front of the circle, with the photographic paper wrapped nearly completely around the circle. Rather than imagine, there are drawings and step-by-step instructions on the http://www.solargraphy.com website. Look for the “how to” link. It will make sense then.